class Solution {
public:
    int search(vector<int>& nums, int target) {
        int left=0,right=nums.size()-1,ans=-1;
        while(left<=right)
        {
            int mid=(right-left)/2+left;
            if(nums[mid]>target)
            {
                right=mid-1;
            }
            else if(nums[mid]<target)
            {
                left=mid+1;
            }
            else
            {
                ans=mid;
                break;
            }
        }
        return ans;
    }
};